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One of the oldest and still most common
kind of heating plant for the home is the coal furnace. A good coal furnace
fired with high-grade fuel will give very satisfactory service with minimum
effort on the part of the owner. When people complain about the work required
to coax heat from their coal furnaces, the fault is generally with the
fuel, the chimney, or the manner in which the furnace is operated.
Efficient operation of any coal-burning
furnace is largely dependent upon the chimney. Any leaks about the chimney
will interfere with the draft and prevent the furnace from working properly.
The stove pipe from the furnace to the chimney should slant upward and
be sealed tightly into both furnace and chimney.
There are many minor points connected with
operating a coal furnace that should not be overlooked, especially if
you are having difficulty in keeping the furnace operating properly.
First of all, put only coal on the fire-never
rubbish of any sort. Ashes should not be used, as they sometimes are,
to bank the fire for the night. Never poke a fire, as this will mix the
hot coals with the ashes and form clinkers.
If the basement is tightly shut, air will
not circulate properly, the draft will be feeble, and the fire will burn
poorly. Check to see that all the furnace doors shut tightly and that
there are no leaks around the check damper when it is closed.
Fuels
There are three kinds of coal used in the
home furnace, anthracite, coke, and bituminous. Anthracite is probably
the most widely used. It is very hard, and because it is low in volatiles
it burns without smoke. It does not tend to swell and cake together as
do some other coals, and it ignites easily.
Coke is similar to anthracite in that it
burns without smoke, and it can be fired in much the same manner.
Bituminous is a soft coal, high in volatiles,
and produces more smoke and soot than anthracite or coke. It is used mostly
for industrial work.
In the United States, coal is graded according
to size by passing it through screens or sieves of different sized mesh
to separate the pieces. Each size is known by a specific name.
The following table shows the diameter of
the mesh through which the largest piece of a given size of coal will
pass. Thus, egg size coal will pass through a mesh which is 3 7/16 inches
in diameter but not through one which is 2 1/2 inches in diameter. Stove
coal will pass through a 2 1/2 inch but not a 1 9/16 inch mesh, etc.
Anthracite
| Name of size |
Diameter of mesh
(inch) |
Broken
Egg
Stove
Chestnut
Pea
Buckwheat (1)
Buckwheat (2) |
4 1/2
3 7/16
2 1/2
1 9/16
1 1/16
1/2
1/4 |
Bituminous
Lump
Egg
Nut
Slack |
more than 4
4
1 1/2
3 /4 |
Sizes of anthracite
The first consideration in burning anthracite
is to get the proper size for the furnace. Anthracite is obtainable in
several sizes, and each size is best suited for a particular firebox.
- Egg size is intended for fire pots not
less than 24 inches wide and at least 16 inches in depth.
- Stove coal is suited for fire pots 16
inches wide and 12 inches deep. Most home furnaces are designed to burn
stove coal.
- Chestnut is made for kitchen stoves and
hot water boilers, where the fire pot is 10 to 16 inches deep and approximately
20 inches in diameter, and for furnaces with this size firebox.
- Pea coal is used for kitchen ranges and
water heaters, and can be used in the furnace, provided there is an
excellent natural draft and special care is taken, when shaking the
grates, not to allow the hot coals to fall.
The very small sizes, No. 1 buck wheat and
No. 2 buckwheat, are intended for use in heating equipment with mechanical
stoking devices and forced-draft blowers.
What size to burn
Coal, or any fuel for that matter, must have
air if it is to burn. Large-sized coal, when put in the firebox, will
not pack very close together, and there will be ample space between each
piece of coal for the circulation of air. Air enters from the bottom of
the fire and must work its way through the entire fire bed. Small-sized
coal, put into a fire pot, packs to-together so that only a small amount
of air can penetrate. If only a little air circulates, the fire will burn
poorly and go out. Small-sized coal can be used for kitchen ranges or
hot water heaters because the fire bed is not very deep.
While each furnace is best suited for one
size of coal, it is possible to use a smaller size. This is generally
done for the purpose of economy, as the smaller anthracite coals are somewhat
cheaper per ton than the larger sizes. Using smaller coal is also a very
good means of retarding the fire during warm weather. Lastly, it is sometimes
impossible to get the larger coal, and then the small sizes must do. When
burning chestnut and pea coal, a somewhat thinner bed is required. These
small coals pack quite densely, and if you try to build up a full fire
pot with them, the fire will not burn very well. Probably the best method
of burning small coal is to mix it with the regular size. This is done
by putting on a layer of stove coal and then adding a layer of the smaller.
Start the fire with stove coal, and when this is burning well, add the
first layer of small coal. In a furnace, the fire bed is many inches thick,
and if small-sized coal is used exclusively, a blower should be provided
to force the air up through the fire bed.
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